Integration of Canopy and Hydraulic Architecture in Neotropical Shrubs Along Light and Moisture Gradients

9604424 Pearcy本研究将调查植物树冠的水力学与树冠上用于光捕获的叶面积的数量和排列之间的相互关系，使用Psychotria属的物种，灌木的一个突出属。 基本的假设是，有一个权衡之间的最大限度地提高光捕获和提供足够的茎电导率，以供应水分的叶子，这种权衡不同的物种之间的地区适应干旱和物种适应地区或多或少永久潮湿。 要利用的物种发生沿着栖息地梯度的光和鱼苗季节的严重程度，使选择压力水力学与光捕获将在他们之间不同。 一个可以重建植物三维结构的计算机模拟模型将被用来估计不同物种的树冠结构的光捕获能力和效率。 将确定茎的水力传导率和对空化的脆弱性，空化是在木质部中形成气泡，阻碍水流并可能导致芽死亡。 最后，干水力传导将映射到冠架构和模拟中使用，以探讨不同的干旱情况下的空化脆弱性的物种差异的后果。 这项研究将提供深入了解如何的功能形态的冠，最明显的表现形式的物种差异，涉及到物种分布沿着光和水分梯度。 由于光照和湿度梯度是热带森林生物多样性的重要决定因素，这项研究将最终深入了解这些森林生物多样性的功能控制。

9604424 Pearcy This research will investigate the interrelationships between the hydraulics of a plant crown, and the amount and arrangement of leaf area on that crown that functions for light capture using the in species of the genus Psychotria, a prominent genus of shrubs. The basic hypothesis is that there is a tradeoff between maximizing light capture and providing sufficient stem conductivity to supply water to the leaves and that this tradeoff differs between species adapted to areas subject to drought and species adapted to areas more or less permanently wet. The species to be utilized occur along habitat gradients of light and fry season severity so that the selective pressures for hydraulics versus light capture will differ among them. A computer simulation model that can reconstruct the three-dimensional architecture of a plant will be used to estimate the light capture capacity and efficiency of the crown architectures of the different species. The stem hydraulic conductances and the vulnerability to cavitation, which is the formation of air bubbles in the xylem that blocks water flow and can lead to death of the shoot, will be determined. Finally, stem hydraulic conductances will be mapped onto the crown architectures and used in the simulations to explore the consequences of species differences in the vulnerability to cavitation under different drought scenarios. This research will provide insight into how the functional morphology of the crowns, the most visible manifestation of species differences, relates to species distribution along light and moisture gradients. Since light and moisture gradients are important determinants of biodiversity in tropical forests the research will ultimately provide insight into the functional controls on biodiversity in these forests.